There are many types of topical antiperspirant products that are commercially available or otherwise known in the antiperspirant art. These products typically contain an antiperspirant active in the form of an aluminum and/or zirconium salt and which are formed by the partial neutralization of acidic aluminum (Al+3) and zirconium (Zr+4) metal ions. The partial neutralization results in the formation of aluminum and zirconium hydrolysis polymers of complex structure. Without being bound by theory, it is believed that these actives reduce perspiration flow to the skin surface by forming shallow blockages within the sweat ducts that carry the perspiration to the skin surface.
Aluminum-only salts may include aluminum chloride and basic aluminum salts such as aluminum chlorohydrate, aluminum sesquichlorohydrate and aluminum dichlorohydrate. Often, these aluminum salts are mixed with zirconium salts (e.g., zirconium hydroxy chloride) to make combination salts such as aluminum zirconium trichlorohydrate and aluminum zirconium tetrachlorohydrate. Aluminum zirconium salts are generally believed to be more efficacious than aluminum-only salts due to the more acidic nature of zirconium salts in the mixture. Without being bound by theory, the increased acidity is believed to increase the lifetime of the blockage that provides the reduction in perspiration flow.
To improve the efficacy of aluminum-only actives such as aluminum chlorohydrates, one can control the process of making the actives in order to provide a higher concentration of lower molecular weight hydrolysis polymers. It is generally accepted that actives with higher concentrations of Band III polymers, as measured by gel permeation chromatography, have higher efficacy. Thus, there are many methods known in the art to increase the level of Band III polymers including heating or aging actives. When aluminum salts possessing a high level of Band III polymers are used to produce aluminum zirconium salts, an efficacy increase occurs thereby providing actives that are typically more efficacious than aluminum-only actives having similar levels of Band III polymers.
While aluminum zirconium salts are desirable as an antiperspirant active, the increasing costs of zirconium raw materials may impede or prohibit the use of such materials in products. Moreover, zirconium salts are prohibited for use in aerosol products, which are the preferred product form in some markets. Thus, there is a need to improve the efficacy of aluminum-only salts such that they are equal to or exceed the efficacy of aluminum zirconium salts with high levels of band III polymer.
Accordingly, the present invention provides an enhanced efficacy antiperspirant active using an improved aluminum-only salt and a process for making the active. Particularly, the present invention provides an enhanced efficacy antiperspirant active comprising an improved aluminum-only salt having a Band III level polymer of at least about 20% and comprising a level of monomeric aluminum ranging from about 2% to about 20% of the total aluminum wherein the aluminum to anion ratio is from about 1.1:1 to about 1.8:1. Furthermore, the present invention provides a process for making an enhanced efficacy aluminum-only salt active by providing a solution of an aluminum hydroxyhalide salt having at least about 20% of a Band III polymer, mixing with a solution of a monomeric aluminum salt and rapidly drying the mixture to form a product powder.